Mating patterns of different Adh genotypes of Drosophila melanogaster. II. Testing rare-male mating advantage.

In this paper we analyze the rare-male mating advantage at the Adh locus in Drosophila melanogaster by three different statistical methods: chi 2 test [classically applied for this kind of experiment (Ehrman, 1966; Spiess and Schwer, 1978; Markow et al., 1980)], linear regression (Adams-Duncan's test), and estimation of relative male mating success (Anderson-Browns's test). With the chi 2 test, a rare-male SS mating advantage could be speculated in the FF vs. SS comparison, but when the other two statistical methods were applied, this effect was not evident. However, in the FF vs. SS comparison, FF males show a much greater mating success than SS males in experiments with a 1:1 or 1:9 ratio. In the FF vs. FS and FS vs. SS comparisons, differences in mating success and frequency dependent selection were not found. The fact that a rare-male mating advantage is not detected for any of the Adh genotypes seems to indicate that this type of frequency-dependent selection is not a major component of the mechanism to maintain polymorphism at the Adh locus.